Rust Sea

The Rust Sea is an area of unstable planetary matter and molecular flux located along Cybertron's equator. Or in simple terms, it's exactly what its name implies. It's a sea, but it's not full of water.

The Hydrax Plateau rises out of the center of it. Cybertron's primary spaceport is located here, where planetary visitors must check in first.

From Teletraan I: The Transformers Wiki, a Wikia wiki.